Radioreceiver



Jam .28, 119336. M. PERKINS ZZBES RADIORECEIVER Filed May l3l, 1930 w will@ m Patented Jan. 28, 1936 UNITED 'STATES .lRDIORECEIVER Laurence SM. Perkins, .Da

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America, New York, Delaware yton, Ohio, assignor, by o Radio Corporation of N. Y., VVa corporation of Application May 31, 1930, .Serial.No. 457,728

2 Claims.

This invention relates to'aniautomaticwvolume control for a radio receiver.

An object of this invention is to provide an automatic volume control that makes the potential supplied to the grids to some of the tubes more positive as the signal decreases and vice versa.

Another object of this invention is to provide an automatic volume control in connection with the radio receiever having a pentode output tube.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawing, wherein a prefered embodiment of one form of the present invention is clearly shown.

In the drawing:

The single figure discloses a schematic wiring diagram of the preferred modication.

The reference characters I0 and I2 indicate the screen grid tubes in the two stages of radio frequency amplification, I4 the detector tube in the detector circuit and I6 a pentode tube in the audio-frequency stage of amplification.

The grid circuits including the grids 2 I, 23 and 25 of the tubes I0, I2 and I4 may be tuned to the same resonance frequency by adjusting the tuning condensers 20, 22 and 24 in parallel with coils 30, 32 and 34, respectively.

Plate voltage is supplied from a B-source to the plates 36 and 38 through the resistances 40 and 42, respectively, and the coils 44 and 46, respectively. The plate circuits 36 and 38 are connected to the succeeding grids 23 and 25, by coupling loops 48 and 50 to the coils 32 and 34.

A suitable potential is supplied to the space charge or screen grids 52 and 54 from the B- source through the resistances 56 and 58, respectively. In the grid circuit of the detector I4, the condenser 60 is provided with a grid leak 62 connected to a single tap of the resistance 64, placed in parallel with the A-battery. 'I'he resistance 64 has been provided so that the interchanging of the terminals of the A-battery will have no eiect upon the detector circuit. This is found especially desirable where radio receivers are installed on motor' vehicles such as passenger automobiles or busses, and Where the filaments are energized from the storage battery of the motor vehicle. The battery 66 in series with a portion of the resistance or potentiometer 68 supplies a potential to the space charge grid 'I0 of the detector I4. This potential supplied to the space charge grid 'l0 may be varied by changing the tap 'I2 on the variable resistance 68.

In the particular modication disclosed, the detector I4 is provided with a grid 14 that is connected :to theimiddle Yof the lament Within the tube.

The grid of the audiofrequency amplier or realy is supplied by a C-potential through the battery 82, connected to the plate circuit 84 of the detector I4 that is supplied by space charge current through a resistor 86 from a suitable B-supply. The audio tube I6 is also provided with a space charge grid 88 supplied by a suitable B- potential through the choke 90 and a cathode grid 10 92 connected to the lament 93. The cathode grid 92 interposed between the space charge grid 88 and the plate 94 probably functions to prevent secondary emission from the plate 94.

The condensers |00, |02, |04, |86, |08, |09, ||0, 15 and ||2 act as by-pass condensers for radiofrequency currents. The B-potential is supplied to the plate 94 through a choke I|4 that prevents the audiofrequency currents of the plate 94 from passing through the B-source and aids in causing 20 the audio currents to pass from the plate 94 through the large condenser ||6 connected to a suitable signal reproducer, not shown.

In the modification disclosed, a B-battery has been shown that supplies a B-potential to the 2.5 plates and the screen grids of the radiofrequency tubes and the plates of the detector and the tube in the audio relay. Instead of a B-battery any other suitable source of potential may be used. The potential supplied to these several elements 30 is not equal to the potential across the terminals of the B-battery, for the reason, that this is reduced by the potential drop across the resistance |20, connected intermediate the negative terminal of the B-battery and the ground. In 35 the operation it is preferable to have the potential drop across the resistance |20 substantially equal to the voltage across a portion of the B- battery indicated by the reference character |22 that has the positive terminal connected in se- 40 ries with the parallel resistances |24 and |26 leading to the grids 2| and 23, respectively, so as to supply a suitable potential to these grids.

Operation of automatic volume control An increasing incoming signal causes a decrease in the plate current in the detector I4, probably due to a greater number of electrons physically striking the grid 25 so as to increase the grid current through the resistance 62, thereby making the grid potential more negative. Of course, as the potential on the grid 25 goes more negative, the plate current in the plate circuit 84 is decreased and as this plate current decreases the potential drop across the resistance 55 86 decreases so that the potential of the grid 810 is actually more positive when the incoming signal is increased. This increase of the potential of the grid 80 causes an increase in the plate current in'the tube I6 which carries, by far, more current than any other one of the tubes and dominates the change of potential across resistance 20. Consequently the current through the resistance |20 is increased so as to increase the voltage drop across the resistance that results in a more negative potential being supplied to the grids 2| and 23, thereby automatically reducing the amplification of the increased incoming signal so as to maintain substantially a uniform volume output. This volume output may be changed by adjusting the tap 12 on the potentiometer 68.

While the form of embodiment ofthe present invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted, all coming Within the scope of the claims which follow.

What is claimed is as follows:

1. In combination with a radio receiver of the type includingra high frequency amplifier, a detector including a tube provided with a screen grid electrode, and an automatic gain control connection between the plate circuit of the detector and a gain control electrode of said amplier, aV source of positive potential for said screen grid, and means for adjusting the screen grid potential to regulate the volume output of said receiver.

2. Incombination with a radio receiver of the type including a high frequency amplifier, a detector including a tube provided with a screen grid electrode, and an automatic gain control connection including a direct current amplier between the plate circuit of the detector and a gain control electrode of said amplier, a source of positive potential for said screen grid, and means for adjusting the screen grid potential to regulate the volume output of said receiver.

LAURENCE M. PERKINS. 

